All things mtb

[deacon]

I just might finally have this bike together.

friction clutch is no more than the motor on a hinge. A cable from the extra brake lever (tossed out the adjuster so it was full throw, thanks to bike guy joe)...
I cut off all but three inches of the sheath and ran the pure cable to the front of the engine mount. The brake lever at full throw seems to lift the engine just enough to disengage it. To adjust it I simple rotate the lever on the bar. I can tight or loosen it quite a bit. I also removed the hex nut and bolt which locks it to the handle bars. I replaced it with a quarter inch one. I used quarter inch for everything else so it is easier to work on should I be out when it needs adjusting.

I finally got the right spring so it will pull all the time not skip and yet not so much that I can't lift the engine. I need to test ride it on a the long test course a little later but it seem to be just fine.

I think it will pull most of the hills without pedaling but I will probably do so now and then anyway to keep the speed up a bit.

 

[deacon]

I just got back from my latest test ride. I found a huge crack in the pot alum housing of the ww motor. I stuffed it full of jb weld for now. I think the next one I get I'm going to go ahead and put spacers in the metal and drill new holes. The factory ones are just too weak. They were never meant to support the engine like that.

I"m also beginning to think tiller motor... I promised I would not build another bike so I give that thought away. The WW is fine but never meant to be mounted stationary. Still it does work well.

Oh by the way they run like crap on half choke... Yes I forgot to move it up again. Once I did it ran a whole lot better.

 

[deacon]

after I declared the chainsaw a spruce goose, I took a ride on the mtb. It was doing so well that I ran it hard and it rewarded me by the engine flying apart. I swear the drive wheel broke the drive shaft and off popped the flywheel. It was quite a sight to see. Fortunately I was only a couple of blocks from home. That was a brand new bolens whacker motor two. Unfortunately the drive wheel was not balanced.

I learned a lesson today. More than one actually. If it vibrates really badly and you ride it anyway, you are asking for trouble. Now that I have learned that I know what happened and why.

So the mtb is history since I don't really like the brake system anyway. I will salvage what I can from it I guess, or maybe leave it as is just in case I decide to build on it again.

Tomorrow I'm going to start looking for a new motor. I can't sit around with only one bike I want to ride. The chainsaw bike isn't something I enjoy so it is just for a paperweight I think.

 

[jasonh]

Deacon you should see if you can pick up a small portable generator somewhere for cheap and see what you can do with it

 

[deacon]

I have all these ebike parts laying around that I used to use.... generator hmmm.

 

[jasonh]

Well I was thinking yank the motor off the generator, but you could set up a hybrid type of system. Make it an e-bike, and have the generator charge the batteries while you ride when they get low.

 

[Dave31]

This was my suggestion but he did not go for it

 

[jasonh]

hahaha. Somehow I doubt you'd be able to get enough airflow to get that turbine going. Though I guess if you had a lightweight one designed to be used in 15-20mph wind, it might work.

 

[deacon]

Guys guys guys lol

On the serious side, I put the 25cc on the bike of course it won't start. I did start before I improved it lol.

I changed the carb from one with an off on to one with a throttle adjustment. Except for the throttle adjustment it is the same darn carb. And the carb worked on the last motor just fine. Now nothing.

I just put the old one back on. I am going to wait until tomorrow to hook up the gas lines and give it a try. If I don't stop right now I will be up all night with it.

It does have a blue spark and the plug is soaked. Obviously the better carb is flooding it somehow. Oh Well tomorrow will tell the tale.

 

[deacon]

Okay it's back from the ashes lean and mean. lol..

I had a 25cc engine I was messin with so I got it to run last night and put it on the bike just as the 31 had been but running the way it was intended. For a drive wheel I am using a bmx textured axle peg of about an inch diameter. The bike runs very very well.

I really can tell very little differnce on the test ride but (and its a big one) the bike only ran wide open throttle and the muffler blew off and took some of the supports with it.

Norman would be proud of me. I tied the muffler to the handle bars with the pull rope and brought it home. Screaming like a banshee all the way.

I was pleasantly surprised by the power of the engine on the hills. Not a lot of difference between the two engines far as I can tell. I don't have a lot of tension on the wheel so it didn't seem to bog down at all.

All in all it might do very well for a little helper motor, That is if I can get the throttle issue fixed. And of course put the muffler back on it. I'm waiting for it to cool down before I try to fix it.

 

[deacon]

After all that I think I have a bike I like pretty well. It isn't as powerfull as the 31cc but it is reasonably close.

I wound up with a 25cc leaf blower engine, but I had to switch the carb to get a throttle. After many retro fitting of the linkage it works very well finally.

The drive wheel is a bmx 1inch od axle peg. The blower engine had a long long drive shaft. The bmx axle peg slipped own over it pretty close. The peg is 3.8 id and the drive shaft is 5/16od... Needed a few washer, double nuts.

It is friction drive with a gravity clutch. I can rope start it in my drive and warm it up. Even start off running that way. If I accidentally choke it off, I can lift the clutch pedal it up to speed then drop the engine and off she goes. Starts right up. Can lift the engine to make turns and to stop at stop signs ect.

The main thing is I killed one 25cc without a clutch because i thought it was starting after a turn but it was really out of gas... NO gas no lube it seized. I got it clear but it knocked so it was the carb donar for this one.

I loved this bike with the 31cc engine and would probably do that again but I did miss the drag start ability of the 25cc. I think you probably could drag start the 31cc if you got up enough speed then dropped the engine and kept pedaling. Even better if going down hill.

One thing I notice is the 31cc idles better than the 25. The 25 seem to choke down a lot easier.

I do have the 33cc chainsaw bike to work on next. I know i pronounced it complete but my neighbor finally got the smaller drive wheel welded. I want to try the bike with it. I also want to tighten down and lock the motor frame. I might be able to get rid of the vibrations.

 

[deacon]

Bike with new engine

new engine and no welding mount. note the peanut butter jar lid air filter... the cable lift mechanism. The scissor henge to keep the motor straight but allow it to lift some. Spring to give it tension and still allow it to lift.

 

[deacon]

The latest improvement, it seems to be a good one, is a brake cable without the sheath run from the front of the motor mount up through a small hole in the handlebars, then secured onto the top bar into an s hook. The hook is held on with a pipe clamp. The purpose is to hold the engine up while starting.

The problem was that the clutch cable could only be adjusted to lift the engine just enough to clear the wheel. Any more an when the clutch was released it held it up just enough so that it didn't get good traction.

So the new cable holds the engine up far enough for the easily start it, then can be released while holding in the clutch cable. This allows the engine to be engaged when the bike is moving using the brake lever clutch. Simple but very effective.

The small hole in the handlebars was to prevent the cable from working back and getting fouled in the wheel or motor. I may install this same system on the other gravity bikes I build. I think I can do it on the chainsaw bike by attaching it to the lift/drop lever.

 

[deacon]

Well the mtb25 passed the first real world test. It climbed up the worst hill I have on my way to home depot. It will be a usable bike at only 25cc. I am very surprised by that. I thought I would need at least the 31cc to climb that hill but not so. I haven't tried it on the longest hill yet just the steepest one.

Tomorrow morning before the traffic gets bad I'm gonna try that long hill.

 

[deacon]

Just something I thought someone thinking of building my style bike should know.... Starting proceedure.
1. pump the bulb to purge air from the carb
2. Lift engine
3. Hook tie up cable (holds drive wheel about and inch or so above the front wheel.
4. move choke lever to full choke
5. Wrap rope around the drive wheel being sure that it is turning the wheel in the right direction.
6. Since lifting the engine makes the distance from the throttle to the handlebars shorter it creates slack in the cable soooo pull back on the cable.
7. Pull the rope.
8. If the engine does not attempt to start, check the kill switch lol. Then begin again.
9. After the engine tries to fire, move the choke setting to half choke and pull the engine over. It should run at this point. Give it a couple seconds then move it to no choke setting.
10. Hold the clutch lever (brake lever) in while lower the engine.
11. Adjust the throttle
12. start pedaling then release the clutch thus lowering the engine and hold on.

This engine will drag start but since it requires the choke settings I prefer to rope start it. Also trying to drag start it with no gas is how I siezed the last 25cc I had. I will drag start it if it dies at a stop sign and I kNOW it has gas. At that point it is warmed up and starts very easily.

See it ain't easy being me. Benefit of this type setup is you can lift off the wheel and lock it should you need to pedal it home for any reason. Yes it is easier to pedal but also you aren't risking your engine.

 

[deacon]

Today was a test out the bike day. I took it on a ride that would be typical if it were my number one errand bike. I ran it to the shopping center. It did pretty well. I had to pedal about ten strokes to get it up a hill and that was only to keep the speed up.

I also tested it with a trailer to see if it would pull an empty trailer straight. It did just fine with no loss of pull at all. I probably need to add some weight to it, but the trailer i used was very small so I will have to use my bigger trailer to test that later this afternoon maybe.

Anyway here is a picture of it with the smallest trailer I own.

 

[Ranger]

Nice setup, I bet it turns some heads LOL.

Have you tried to put the bike in a low gear and pedal to start it? This may work.

As for your mass production gas tank, have you tried an quart paint can? You can buy them empty, they just have a primer coating on the inside. Not sure if gasoline will eat it up yet.

What kind of speed do you get? I'm guessing only about 16-20 MPH

 

[deacon]

good guess on the speed. It might do a little more than twenty if I had the nerve. I always have to throttle back going downhill.

I bid on some plastic 34 ounce canteens. They should work just fine and be light weight. At least I hope so.

I can drag start it once it is hot if I choke it down. I prefer to rope it first and let it warm up while I sit on it. I would hate to pedal it motor down for a couple of blocks.

I like this bike but I'm yearning to build a 31cc again. I have actually learned a lot and am ready to write my how to instructional book. My grand daughter has a 24" mountain bike that she hasn't ridden in years her mom and dad are begging me to take it just to get it out of their garage. I think I am going to do just that and document a build from scratch as an instructional.

You know lots of pics including ones at the home depot store.

 

[Ranger]

Ok,

I made the gas tank today, it works great. Just some 3/4" copper pipe for the filler and a copper cap for the cap

I'm working on my 31cc right now, I got it running good just need to make some more adjustments.

 

[deacon]

Im looking forward to seeing the pictures and hearing about how you like it. I think the 31cc if you can drag start it is the idea size.

My 33cc chainsaw bike is too heavy. I really did like the 31cc before I shook it apart. It had just a little more balls than this 25cc.